feat(form-builder): retry/resolve/dismiss API endpoints + dual-route auth (WS-6)

Two route groups: /api/v1/admin/form-failures (super_admin platform) and
/api/v1/organisations/{organisation}/form-failures (org_admin scoped).
Same controller, policy authorises via FK chain (RFC V3). Cross-tenant
access returns 404 not 403 to prevent enumeration.

Resolve takes optional note; Dismiss requires DismissalReasonType
enum with conditional note (mandatory for 'other'). Both via
FormRequest validation with explicit i18n message keys.

Implementation note: Laravel implicit model binding for nested-namespace
ULID models doesn't pick up reliably across nested route groups. Using
manual resolveFailure() helper that loads withoutGlobalScopes() (so
cross-tenant access still reaches the policy, which translates denied →
404 per V3). Policy explicitly checks soft-delete via deleted_at since
withoutGlobalScopes bypasses SoftDeletes too. Policy registered
explicitly in AppServiceProvider — auto-discovery doesn't reliably
resolve App\Models\FormBuilder\* → App\Policies\FormBuilder\*.

NOT: admin UI (session 3). Not: public form routes (no API contract
notification needed).

Refs: RFC-WS-6.md §3 (Q5), §4 (V2, V3)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/lang/nl/form_builder.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+return [
+    'dismiss' => [
+        'note_required_for_other' => 'Een toelichting is verplicht wanneer reden = "anders".',
+    ],
+];